The present invention relates to a method for producing woven fabrics, more particularly airbag woven fabrics in making use of a multiphase or series shed weaving machine.
Known from WO 96/38 610 is, for example, a series shed weaving machine with weaving rotor featuring insertion and beating-up reeds. The insertion reeds serve at a periphery to reed warp threads from an insertion station up to a beat-up in the form of sheds when weft threads are fed into the sheds from a weft thread conditioner. The beating-up reeds serve to beat up the picked wefts at the beat-up of the formed woven. With this technology a particularly uniform enlacing of the two warp and weft thread systems is achievable in thus enabling the physical properties of the woven to be equalized over the width of the woven web in avoiding a left/middle/right effect. Although with the simultaneous pick of, for example, up to four weft threads a very high pick capacity of up to 5000 meters per minute materializes in achieving cost-effective weaving at extremely high speed, the material produced on a series shed weaving machine is a woven of less density mechanically.
It is thus an object of the invention to propose a method for producing woven fabrics in making use of a multiphase or series shed weaving machine suitable in density for use as an airbag woven, as well as the woven fabric itself. This objective is achieved by a method as it reads from claim 1. This results in the advantage that in making use of a high-shrinkage type of yarn in the warp direction in the finishing process by hydro- and/or thermoshrinkage the weft density is simultaneous increased. When use is made of a medium to low shrinkage type of yarn as the weft material the shrinking motion in hydro- and/or thermoshrinkage occurs at the binding points asymmetrically such that as a result the finished woven comprises symmetrical thread densities in weft and warp in accordingly featuring in addition to air permeability also the remaining physical properties—the same as the conventionally produced woven—in both thread directions. From a raw woven fabric woven asymmetrically due to the system of the series shed weaving machine a symmetrically structured textile surface area is achieved by finishing which satisfies the density and symmetry requirements of airbag wovens.
The method as set forth in claim 1 is further sophisticated to advantage in that filament yarns having 8-14% and 1-5% hot air shrinkage are used as warp and weft respectively. Making use of these types of yarn results in an end product of exceptionally homogenous weave particularly suitable for use in airbags.